Push button three way switch



April 30, 1957 HUNG-TU TSENG ETAL PUSH BUTTON THREE WAY SWITCH Filed Aug. 23, 1954 mmvrons Hum: -'ru TSENG Yun Tm Mmo AMER/15'):

n e S w Pate 7" PUSH BUTTON THREE WAY SWITCH Hung-tn Tseng and Yun Tai Miao, New York, N. Y.

Application August 23, 1954, Serial No. 451,372-

Claims. (Cl. 200-6) This invention relates to electric switch devices. More particularly, the invention has reference to a device of the nature referred to, that is particularly adapted for controlling the operation of a multi-pole or multi-filament electric lamp. As will appear hereinafter, however, the device is also well adapted to serve as a control means for any lamp fixture or construction comprising two or more lights. The term multi-pole lamp as used herein will be understood to mean a lamp fixture having a plurality of bulbs, as well as one having a single multifilament lamp bulb.

Conventionally, a switching device for a lamp of the type stated is so designed as to require that the user traverse the entire cycle of operation of the switch, in producing a desired condition in the lamp. For example, to turn the lamp on low, the user may have to successively turn the lamp on medium and high, or, to turn the lamp off, it may be necessary to move the switch successively from one position through two other positions. i

This is obviously undesirable, and the main object of the present invention is to produce a desired condition in the lamp, without operating the switch through any switch positions other than the specific position desired.

Another object is to provide a switch device of the nature referred to which will be sure in operation, readily adapted for manufacture in quantity production at relatively low cost, and rugged and trouble free despite its heavy usage over a substantial period of time.

Still another object of importance is to provide a switch device of the nature stated which will be operable with a minimum of effort, the device constituting the present invention being so designed as to make use of a bank of push buttons conveniently located and individually depressible with a minimum of efiort. It is proposed, in this regard, that the depression of any push button will automatically effect the movement to an inoperative position of that one of'the other push buttons which was last depressed. i

For further comprehension of the invention, and of the objects and advantages thereof, reference will be had to the following description and accompanying drawings, and to the appended claims in which the various novel features of the invention are more particularly set forth.

In the accompanying drawings forming a material part of this disclosure:

Fig. 1 is an'exploded perspective-view, portions being ating plates when said plate is in operative.or contact-' closing position.v

2,790,859 Patented 30,

Fig. 3 is an enlarged transverse sectional view on line 3--3 of Fig. 2.

Fig. 4 is a perspective view, on an enlarged scale, of a hold-down spring incorporated in the switch construction.

Fig. 5 is a perspective view of one of the push buttons.

Fig. 6 is a perspective view showing one of the actuating plates in the process of being assembled with associated spacer discs.

Fig. 7 is an enlarged perspective view of one of the spring contact elements.

Fig. 8 is a circuit diagram showing the device in connection with three lamps.

The switch device constituting the present invention can be appropriately considered as having incorporated therein four main components. These are a receptacle or housing 10, a switch assembly mounted in said housing and designated at 12, a cover plate 14, and an end or contact support plate 16.

Considering first the construction of the receptacle 10, this is illustrated in the present'instance as being formed from electrical insulative material, such as plastic. However, this particular portion of the device could, without affecting adversely the switch operation, be fabricated of metal. In any event, the receptacle is of open-topped formation, and includes side walls 18 integral along their lower edges with a bottom wall 20, said bottom wall 20 intermediate its ends being formed with an inclined midlength portion 22, merging into an upwardly olfset rear end portion 24. The end portion 24 is integral with a permanent, non-removable end wall 26 of the casing, said end wall 26 being integrally formed at its upper edge with an elongated ear 28 disposed medially between the sides of the receptacle and extending outwardly from the receptacle, as shown in Fig. 1.

Formed upon the upper edges of the side walls 18 are laterally and outwardly extendnig ears 30, said cars 30 being located adjacent the permanent end wall 26. Each of the cars 30, and the car 28, is formed with a screw-receiving aperture, for a purpose to be made presently apparent.

The cover plate 14 is formed of a flat, generally rectangular piece of material. This can be formed either of plastic or of metal, as desired. In either event, the cover plate includes the body 32 proportioned to close the open top of the receptacle 10. integrally formed upon the opposite side edges of body 32 are cars 34 registering with the cars 30 in the assembled condition of the cover plate and receptacle, the cars 34 having apertures that register with the apertures of said ears 38 to receive screws or similar fastening elements, not shown, whereby the cover plate may be secured to the receptacle, and the entire device may be secured to an associated support, such as a lamp base, or wall of the house, not shown. At that end thereof adjacent the ears 34, the body 32 is formed with an elongated ear 36 extending outwardly from the end edge of body 32 to register with the car 28, again for the purpose of receiving fastening screws or the like. The body32, at its opposite ends, has an car 38 analogous to car 36, having an opening through which ascrew or similar fastening element is extendible. At opposite ends of the ear 38, depending tabs 40 are in tegrally formed upon the adjacent end edge of the body 32, said tabs 40 having openings registering with upper end openings provided in inwardly turned flanges 42 formed upon the adjacent end of the receptacle body. The flanges 42 are located at opposite sides of the receptacle body, the receptacle body being fully open be tween said flanges. Screws or the like would be'extended through the registering openings of the tabs 40 and 3 flanges 42, for the purpose of firmly securing the cover plate in place upon the receptacle 10.

The end plate 44 is formed a rcctan ular piece of non-electrically insulative material such I plastic, having openings at its several corners. The openings at the upper corners of the end plate 4 re,, cr with the upper end openings of the flanges 42 and with the apertures of the tabs 40, thus to permit the fastening screws to secure the cover plate, receptacle, and end plate in assembled relation. The lower corner openings of: the end plate register with lower end openings flanges 4-2, to permit the end plate to be fixedly secured to the re ceptacie at the lower end of said end plate.

On the outer surface of the end plate 44, adjacent the lower end portion thereof, there is disposed a horizontally extending buss bar 46, the buss or connecting bar 46 being fixedly secured to the end plate by conductive rivets or nails 48, 50, 52, respectively, said rivets being spaced apart longitudinally of the bar 46 and extending through the plate. To one of the rivets there is connected one end of a lead 54, said lead 54 extending to one side of a suitable source of an electrical power, such as the ordinary house supply.

Above the bar 46 there is disposed at second connect ing buss bar 56, the ends 58, of which are extended upwardly and are secured to the end plate 44 by rivets 62, 64 respectively. A lead 66 extends from the rivet 64, to one pole of a low power filament 68 of a three-pole incandescent lamp 6?. From the other pole of the low power filament there extends a conductor 70 extending to the other side of the house supply. Immediately above the bar 56 there is provided a shorter connecting buss bar 72, the ends of which are secured to the end plate 44 by rivets 74, 76. These, like the rivets or screws previously described herein, are electrically conductive, and extend fully through the end plate 44. Connected to the rivet 76 is a lead 78 extending through one pole of the high power filament 80 of the lamp 69, the Other pole of: said high power filament being in electrical connection with the conductor 70.

Referring now to Fig. 3, it will be noticed that the rivets or terminals 62, 74 are spaced very closely. The purpose of this arrangement is to permit both terminals 62, 74 to be simultaneously engaged by a single. rclatively Wide, spring contact element 32. mounted upon the inner surface of the contact plate 44, being fixedly anchored at its lower end to said end plate by the rivet 52.

Spaced transversely of the end plate 44 from the relatively wide contact element 82 are narrower contact 1 elements 84, 86, respectively. Element 84 is anchored by and is in electrical contact with the rivet or terminal 50, and element 86 is similarly secured in place by the terminal 48.

Although element 32 is wider than the other elements. all the elements are of the same shape. The shape of each element is best shown in Fig. 7, wherein the element 82 is illustrated per so. As will be noted, the element includes a flat base portion having an opening through which the anchoring rivet extends, said base portion lying flat against the end plate 16. At its other end, the base portion is integral with a downwardly extending portion. said portion being defined by doubling the material of: the element back upon itself. The downwardly extending portion, in turn, merges into an upwardly and outwardly extending free end portion which is normally spaced, shown in Fig. 2, from the surface of the end plate 16.

By bending the material of the element back upon itself in the manner discussed above, the element is given springable characteristics, so as to cause the free end portion thereof to normally be spaced outwardly from the end plate 16, out of Contact with the terminals 62 or 74, 76 or 64, the case may be. If, however, the free end portion of any of the free elements is pressed to- Elcment 82 is (iii word the end plate by shifting one of a plurality of actuating plates to the dotted line position thereof shown in Fig. 2, it will be brought in contact with its associated terminal. Said plates will be described in detail hereinafter. As a result, if for example the element 82 is shifted into contact at its free end with terminals 62, 74, a circuit will be closed through lead 54 from one side of the house supply, to both filaments of the lamps 69, and back to the other side of the house supply, due to the fact that the element 82 bridges the terminals 52, 62, 74.

Thus, the element 82 can be appropriately termed a high or large power contact element.

Should the element 84 be shifted into contact at its free end with terminal 76, the circuit closed will be lead 54, terminal 50, element 84, terminal 76, lead 78, high or strong power filament 80, and back to the source of: power through the conductor 70. In this condition of the parts, the incandescent lamp is at medium strength, and element 84 can thus be termed the medium strength contact element. Element 86 would be the low power element, and would bridge the terminals 48, 64.

Considering now the construction of the switch assembly 12, this includes a plurality of individually rockable com or actuating plates, three of which are associated with the respective elements 82, 84, 86, and the fourth of which is used for deenergizing the lamp completely.

The several actuating or control plates are identical to one another, the plates being designated 88, 90, 92 and 94, respectively. The description of one, accordingly, will sutfice for all.

As will be noted from Fig. 6, each actuating plate is formed, intermediate its ends, with a transverse opening 96 located adjacent the lower edge of the actuating plate, said opening 96 receiving a pivot shaft 98 the ends of which are engaged in transversely aligned openings of the side walls 18. Thus, the several plates are mounted for independent rocking movement about an axis ex tending transversely of the receptacle, said axis being common to all the actuating plates.

The actuating plates are formed of insulating material, such as molded plastic, and are spaced from one another by spacer washers or discs 100. The discs 100 could be formed integrally with the respective actuating plates, but in the illustrated example they are individually formed, and alternate with the actuating plates on the pivot shaft 98, thus to space the several actuating plates equal distances apart from one another, as best shown in Fig. 1.

Each actuating plate is formed at one end with .a relatively wide head portion 102, and at its other end with an upwardly offset tail 104 of reduced width. The end edge of the head portion 102 has a particular formation which is extremely important to the functional characteristics of the invention, and as shown in Fig. 6, said head portion, at the lower end of the end edge thereof, has a rounded nose 106 proiecting longitudinally of the actuating plate to engage the free end portion of the associated spring contact element (see Fig. 2).

The nose 106 merges, at its upper end, into an elongated, straight, generally vertical wall portion 108, which terminates at its upper end in an inwardly extending, generally horizontal shoulder or ledge 110. Ledge 110 in turn merges at its inner end into a relatively short, generally vertical wall portion 112 which terminates at its upper end at the front end ,of a ,gently curved top edge 114 of the head portion 102.

It will be seen that a stepped contour is thus imparted to the end of the head portion .102 with the lowermost step forming a nose which biases the free end portion of the spring contact element into engagement with its associated terminal or terminals 62, 74, 76, or ,64 as the case may be, when the actuating plate is rocked about its axis 98 to the dotted line position shown in "Fig. 2. Further, above this step there is defined a second step offset inwardly relative to the first or lowermost step, the second step merging into a third or uppermost step which is offset inwardly relative to the second step. Thus, there is defined between the uppermost step and the one immediately therebelow an annular recess, for a purpose to be made presently apparent.

Formed in each actuating plate is a longitudinal slot 116, the slot 116 extending within the tail 104, and opening upon the tail end of the actuating plate. The slot 116 is adapted to receive the lower end of a push button member shown to particular advantage in Fig. 5. The push button member associated with each actuating plate includes at its upper end a cylindrical operating element 118 which can be of plastic or the like, having a slot at its lower end in which is fixedly engaged the upper end of a guide bar 120, the guide bar 120 being of flat formation thus to define a shoulder at the intersection of said guide bar and the lower end of the element 118. Guide bar 120 extends loosely Within the slot 116, projecting below the tail of the actuating plate as shown in Fig. 1.

The free or lower end of the guide bar 120 extends through a guide opening 122 of slot-like formation formed in the upwardly offset rear end portion 24 of the bottom wall of the receptacle. The projecting lower end of the guide bar is slit longitudinally, and at one side of the slit is bent laterally to provide a stop finger 124 which will engage the lower surface of the bottom wall of the casing to limit upward movement of the push button (see Fig. 2).

The push button is for the purpose of rocking the actuating plate from its full to its dotted line position shown in Fig. 2, it being apparent that depression of the upwardly projecting end of the push button will be effective to shift the shoulder at the lower end of element 118 into engagement with the top surface of the tail 104, thus to rock the tail downwardly to the dotted line position of Fig. 2.

The elements 118 are disposed in a straight row as shown in Fig. l, and are slidably guided within a corresponding row of circular openings 126 formed in the cover plate.

Each actuating plate has associated therewith a spring which is tensioned to normally exert a downward pull upon. the head portion of the actuating plate, tending to swing the actuating plate from the dotted to the full line positions of Fig. 2. The several springs have been designated by the reference numeral 128, each spring being hooked at its upper end to the lower edge portion of the head part of its associated actuating plate, and being booked at its lower end to an eyelet or hook element engaged in the bottom wall of the casing.

A latching or detent plate is embodied in the switch assembly, and overlies all the actuating plates. The detent plate can, if desired, be formed of metal material, and is shaped as a flat member relatively wide so as to extend over the several actuating plates, said flat member being integral at its leading edge with a joining lip 134 formed by slots 133, to add resiliency and is maintained in contact. with the curved portions 114 of the several actuating plates, by a spring 136.

A pivot shaft 130, engaged at its ends in the side walls 13 abovethe several actuating. plates, is adapted to supportthe latching or detent plate for swinging movement, the detent plate being formed, at that edge thereof remote from lip 134, with transversely spaced sleeves loosely receiving the shaft 130. In the space between the sleeves the spring 136 is provided, said spring being circurnposed about the shaft 130 and being illustrated per se in Fig. 4. As will be noted in Fig. 4, spring 136, at its opposite ends, is provided with forwardly disposed, straight extensions 138 exerting a downward pressure upon the detent plate tending to swing the same downwardiy about the axis of the pivot shaft 130. Medially between its ends, the spring 136 is formed with a rearwardly projecting portion 142 having .a hook-like formation at its free end engaged about an anchoring shaft .140, the ends of which are eugagedin transversely aligned openings .of the .side walls 18. Shaft 140, besides engagingportions v142, acts as an abutment limiting upward swinging of the tails-of the actuating plates.

By reason of this arrangement, each time the lip 134 is swung upwardly, the spring 136 will be placed under increased tension, so as to maintain the plate 132in engagement with the upper edges of the several actuating plates.

The operation of the device may now be readily understood, and it is first believed worthy of note that the upper ends of the several push buttons are marked with suitable indicia to designate the function of the particular push buttons. Thus, that push button shown at the far left in Fig. 1 has the indicium 0, meaning off." The indicia L, M and S on the remaining push buttons respectively signify large, medium and small.

The depression of any push button will cause any other push button which was previously in depressed position to move upwardly to inoperative position. In Fig. 1, it may be noted, none of the push buttons is depressed, but in use of the device, there would always be one push button in depressed position. Assuming, for example, that the push button 0 was pressed, the plate 94 associated with said push button would be rocked upwardly to the dotted line position in Fig. 2, and would be held in said position by engagement of the lip 134 in the recess of the head portion of the actuating plate. The engagement of the lip 134, against the vertical wall 112 of said recess is such as to prevent the pull of the spring 128 from asserting itself, thus holding the plate 94 in its 7 dotted line position.

The remaining plates will be in the full line positions of Fig. 2, and as a result, the contact elements 82, 84, 86

will be in open position, and will not bridge their associated terminals.

Assuming that it is desired to turn the lamp 69 on small, push button S would be depressed. During the initial downward movement of push button S, the head part of actuating plate 88 moves upwardly to an extent suflicient to swing the detent plate upwardly to a slight extent. This upward movement of the detent plate, during the initial movement of push button S to depressed position, causes the lip 134 of the detent plate to move out of frictional engagement with the wall 112 of the actuating plate 94. As a result, the spring 128 associated with plate 94 pulls the plate 94 downwardly in a snap action.

Full depression of push button S will, meanwhile cause the lip 134, to engage in the recess of actuating plate 88, to hold plate 88 in its operative, contact-closing position shown in dotted lines in Fig. 2. As a result, the contact element 86 will be moved to terminal-bridging position, and a circuit will be closed through the low filament 68 of the incandescent lamp.

The depression of any other push button will be effective to move the push button last previously depressed to inoperative position, of course, and whenever the incandescent lamp' is to be turned on large, the push button L is depressed, causing both filaments 68, to be ener gized simultaneously.

In no case, of course, is it necessary that the switch be moved through any positions not desired at the particular moment.

In Fig. 8. there is shown a preferred circuit in which the device is shown as a control for operation of three lamp bulbs. In this arrangement, a lead 144 extends from connectingbar 72 to lamp bulbs 146, 148, a lead extending from said lamp bulbs back to the source of electric power. A lead 152 extends from connecting.

bar 56m a lamp bulb 154. The three'lam'p bulbs can all be part of a single fixture and ifa small amount of light is desired, depression of the button will cause a flow of power from lead 54 through contact 86, lead 152, bulb 154 and back to the power source through lead 150. For -medium illumination, one depresses button M to cause flow from lead 54 through contact 84, bar 72, lead 144, bulbs 148, 146, and back to the source through lead 150, thus illuminating two bulbs. For a large amount of il- 'lumination, one energizes all three bulbs by depressing button L," causing flow from lead 54 through element '82, connecting bar 56, lead 152, bulb 154 and back to the source, simultaneously with flow through bar 72, lead 144, and bulbs 146, 148.

For purposes of safety a plate 156 of non-electrically conductive material is secured to the outside of plate 16,

and is formed on its inner surface with recesses 158, 160

suitably shaped to receive bars 56, 72, and 46, together with their associated leads.

' While we have illustrated and described the preferred embodiment of our invention, it is to be understood that we do not limit ourselves to the precise construction herein disclosed and the right is reserved to all changes and modifications coming within the scope of the invention as defined in the appended claims.

Having thus described our invention, What we claim as new, and desire to secure by United States Letters Patent is:

l. A switch for multipole incandescent lamps, comprising a hollow housing, a contact plate mounted at one end thereof, a plurality of spaced terminals for electrical conductors supported on one face of said plate, a plurality of stationary contacts connected to said terminals and extending to the opposite face of the plate, a plurality of other contacts supported on said opposite face of the plate and being connected to certain of said terminals, each of said other contacts having a fixed base portion and a free flexible end portion spaced from the base portion, a plurality of spaced insulated actuating plates pivotally mounted in the housing, the number of said actuating plates being one more than the number of said other contacts, each of said actuating plates having a stepped cam surface with a nose portion and a recessed portion, each of said actuating plates except one being shiftable to an operative position whereby one of said flexible end portions is biased to a terminal bridging position, and a flat spring biased detent plate having cut-out slots overlying said actuating plates, a plurality of push button members for selectively rocking each one of said actuating plates, said fiat detent plate being so disposed that the recessed portions of the actuating plates become engaged in said cut-out portion when the actuating plates r are rocked, the actuation of any one of said actuating plates by a push button member serving to release any other actuating plate engaged in a cut-out slot of the fiat plate.

2. A switch for multipole incandescent lamps, comprising a hollow housing, a contact plate mounted at one end thereof, a plurality of spaced terminals for electrical conductors supported on one face of said plate, a plurality of stationary contacts connected to said terminals and extending to the opposite face of the plate, a plurality of other contacts supported on said opposite face of the plate and being connected to certain of said terminals, cach of said other contacts having a fixed base portion and a free flexible end portion spaced from the base portion, a plurality of spaced insulated actuating plates pivotally mounted in the housing, each of said actuating plates having a stepped cam surface with a nose portion and a recessed portion, each of said actuating plates except one being shiftable to an operative position whereby the nose portion of the shifted plate biases one of said flexible end portions to a terminal bridging position, a flat spring biased detent plate having cut-out portions overlying said actuating plates, and a plurality of push button members for selectively rocking each one of said actuating plates, said flat detent plate being so disposed that the recessed portions of the actuating plates become engaged in said cut-out portion when the actuating plates are rocked, the actuation of any one of said actuating plates by a push button member serving to release any other actuating plate engaged in a cut-out portion of the fiat plate, each of said actuating plates having a slotted tail portion for receiving and engaging a lower flat portion of a push button member.

3. A switch for multipole incandescent lamps, comprising a hollow housing, a contact plate mounted at one end thereof, a plurality of spaced terminals for electrical conductors supported on one face of said plate, a plu rality of stationary contacts connected to said terminals and extending to the opposite face of the plate, a plurality of other contacts supported on said opposite face of the plate and being connected to certain of said terminals, each of said other contacts having a fixed base portion and a free flexible end portion spaced from the base portion, a plurality of spaced insulated actuating plates pivctally mounted in the housing, the number of said actuating plates being one more than the number of said other contacts, each of said actuating plates having a stepped cam surface with a nose portion and a recessed portion, each of said actuating plates except one being shiftable to an operative position whereby the nose portion of the shifted plate biases one of said flexible end portions to a terminal bridging position, a flat spring biased detent plate having cut-out portions overlying said actuating plates, a rod carrying said spring and disposed transversely across said actuating plates, and a plurality of push button members for selectively rocking each one of said actuating plates, said flat detent plate being so disposed that the recessed portions of the actuating plates become engaged in said cut-out portion when the actuating plates are rocked, the actuation of any one of said actuating plates by a push button member serving to release any other actuating plate engaged in a cut-out portion of the fiat plate, said rod serving to limit rocking movement of said actuating plates, and a plurality of springs respectively biasing said actuating plates to inoperative positions when said actuating plates are out of engagement with said detent plate.

4. A switch for multipole incandescent lamps, comprising a housing, a contact plate mounted on one end thereof, a plurality of contact elements and terminals on said contact plate, said elements being adapted in one position thereof to bridge associated ones of said terminals, a plurality of fiat actuating plates movably mounted in said housing and individually associated with the respective contact elements, said actuating plates being shiftable to an operative position in which they bias their associated contact elements to terminal bridging positions, each actuating plate being rockably mounted within the housing for movement to and from said operative position. thereof and rocking independently of any other actuating plate, each actuating plate having a cam surface with nose and recessed portions, said nose portion being in engagement with a flexible portion of a contact element associated therewith and arranged to bias said associated contact element to terminalbridging position ing the same to its operative position, and a flat detent' plate common to and overlying all of the actuating plates, said detent plate having slots arranged to engage the recessed portions of the actuating plates to releasably hold the same in said operative position, the movement of each actuating plate to an operative position serving to raise said detent plate against a spring bias and free the detent plate from engagement in the recess of any other actuating plate.

5. A switch for multipole incandescent lamps, comprising a housing, a contact plate mounted on one end thereof, a plurality of contact elements and terminals on stud contact plate, said elements being adapted in one position thereof to bridge associated ones of said terminals, a plurality of flat actuating plates movably mounted in said housing and individually associated with the respective contact elements, said actuating plates being shiftable to an operative position in which they bias their associated contact elements to terminal bridging positions, each actuating plate being r-ockably mounted within the housing for movement to and from said operative position thereof and rocking independently of any other actuating plate, each actuating plate having a cam surface with nose and recessed portions, said nose portion being in engagement with a flexible portion of a contact element associated therewith and arranged to bias said associated contact element to terminal-bridging position on rocking of the actuating plate to operative position, a push button member having a shoulder portion associated with a tail portion of each actuating plate for rocking the same to its operative position, a flat detent plate common to and overlying all of the actuating plates, said detent plate having slots arranged to engage the recessed portions of the actuating plates to releasably hold the same in said operative position, the movement of each actuating plate to an operative position serving to raise said detent plate against a spring bias and free the detent plate from engagement in the recess of any other actuating plate, and a plurality of springs biasing said actuating plates to said inoperative position when the actuating plates are free of said detent plate.

References Cited in the file of this patent UNITED STATES PATENTS 732,201 Little June 30, 1903 1,008,392 Tiffany Nov. 14, 1911 1,008,514 Armstrong Nov. 14, 1911 1,106,432 Wilcox Aug. 11, 1914 1,977,124 Genrich Oct. 16, 1934 2,069,632 Thomas Feb. 2, 1937 2,144,705 Ober Ian. 24, 1939 2,203,279 Graves June 4, 1940 2,217,395 Wertzheiser Oct. 8, 1940 2,457,153 Hubbell Dec. 28, 1948 2,572,622 Hollinshead Oct. 23, 1951 2,623,958 Loge Dec. 30, 1952 FOREIGN PATENTS 354,393 Italy Nov. 20, 1937 

